One of the techniques used in DEXA is to estimate BMD (bone mineral density) of vertebrae from AP (anterior/posterior or posterior/anterior) view measurements of x-ray attenuation at two different x-ray energy ranges. For example, when a supine patient is between an x-ray source below (or over) and an x-ray detector above, the detector can obtain sufficient information for a DEXA AP view of the spine, or of part thereof, from measurements of x-ray attenuation due to passage of the x-rays through the patient. The DEXA x-ray dosage typically is much less than for a diagnostic image, but the DEXA image still contains enough information from which BMD and other parameters can be estimated. If the BMD or some other parameter for a particular vertebral region in the AP image is desired, the region is delineated, for example by having an operator draw the outline of the region on a screen displaying the AP image. The assignee of this patent specification has manufactured and sold such DEXA equipment for years, including under the trade name QDR. See, e.g., commonly assigned U.S. Pat. Nos. 5,778,045 and 5,432,834, which are hereby incorporated by reference.
Another DEXA technique is lateral vertebral morphometry, in which a lateral rather than an AP image of vertebral bodies is obtained and its information is used, in turn, to obtain measurements or estimates of the size and/or shape of vertebral bodies. One example of DEXA morphometry is described in commonly owned U.S. Pat. No. 5,850,836, which is hereby incorporated by reference, and a morphometry option has been available for years from the common assignee, Hologic Corporation of Bedford, Mass. Another type of morphometry is discussed in U.S. Pat. No. 5,228,068 and a DEXA morphometry capability also has been available in this country for years from that patent's assignee, Lunar Corporation of Madison, Wis.
Another technique used in DEXA is to identify regions of interest in hip images, e.g., areas of interest in AP projection images of the left or right hip. These regions of interest may comprise a global region and sub-regions within this global region.